Created attachment 140281 [details] Left is before adding, right is after adding SUMMARY After adding "Invert Selection" to "Current actions" in "Configure Toolbar", it will be displayed in English.
Confirmed in b00b0063 (Using German 'Auswahl umkehren') Doesn't seem to affect all actions, though, just this one.
I just found out that this bug has been fixed in 5.1.0-RC1. So I changed to fixed.